In the known centerless grinding process for workparts such as bearing raceways, the axes of the workpart and grinding wheel may have to be varied relative to one another in some cases to grind a particular taper on the workpart and in other cases to compensate for wheel deflection or wear or other fluctuations in grinding process parameters during a run causing out of tolerance workparts.
In one commercially available centerless grinding machine, the ability to adjust the axes of the workpart and grinding wheel is provided by mounting the workhead on a pivotable plate. The plate is pivotable about a stationary pivot stud extending between the plate and a cross-slide mounted on the machine base. The cross-slide includes a semi-circular shaped inverted T-slot to receive a pair of T-nuts. Locking screws extend from the workhead into the T-nuts and are manually tightened to lock the position of the workhead and thus the orientation of the workpart axis relative to the axis of the grinding wheel mounted on another cross-slide. Other than the placement of lubricant between the workhead support plate and cross-slide supporting the plate, no provision is made for reducing friction therebetween during pivoting.
To vary the relationship of the workpart axis and grinding wheel axis from parallel to angular to intentionally taper grind or to compensate for changes in grinding parameters, the operator must manually loosen the locking screws and manually turn an adjusting screw which is screw mounted on the workhead cross-slide and engages the support plate. As the adjusting screw is turned, the support plate is pivoted about the pivot stud to the desired position. An indicator dial driven by the rotation of the adjusting screw can be read to determine when the angular relationship of the workpart axis to the grinding wheel axis is established. Thereafter, the locking screws are re-tightened by the operator to maintain the adjusted position. Of course, this adjustment sequence for placing the workpart axis and grinding wheel axis in related angular relationship is time consuming and costly.
U.S. Pat. No. 3,874,121 issued Apr. 1, 1975 shows an internal grinding machine having a swivel base on which a spindle is carried so that the spindle axis can be adjusted angularly.
U.S. Pat. Nos. 4,186,529 and 4,115,956, issued Feb. 5, 1980 and Sept. 26, 1978, respectively, illustrate a programmably controlled machine with a grinding wheel support system and workpart support system each having a plurality of slides and cross-slides and a rotary table driven by individual servomotors for grinding end cutting tools and the like.
U.S. Pat. No. 4,293,913, issued Oct. 6, 1981, discloses a numerical controller for a grinding machine for cylindrical workparts.